Endoscopic surgical instruments are often preferred over traditional open surgical devices since a smaller incision tends to reduce the post-operative recovery time and complications. Consequently, significant development has gone into a range of endoscopic surgical instruments that are suitable for precise placement of a distal end effector at a desired surgical site through a cannula of a trocar. These distal end effectors engage the tissue in a number of ways to achieve a diagnostic or therapeutic effect (e.g., endocutter, grasper, cutter, staplers, clip applier, access device, drug/gene therapy delivery device, and energy device using ultrasound, RF, laser, etc.).
Known surgical staplers include an end effector that simultaneously makes a longitudinal incision in tissue and applies lines of staples on opposing sides of the incision. The end effector includes a pair of cooperating jaw members that, if the instrument is intended for endoscopic or laparoscopic applications, are capable of passing through a cannula passageway. One of the jaw members receives a staple cartridge having at least two laterally spaced rows of staples. The other jaw member defines an anvil having staple-forming pockets aligned with the rows of staples in the cartridge. The instrument commonly includes a plurality of reciprocating wedges which, when driven distally, pass through openings in the staple cartridge and engage drivers supporting the staples to effect the firing of the staples toward the anvil.
An example of a surgical stapler suitable for endoscopic applications is described in U.S. Pat. No. 5,465,895 to Brian D. Knodel, Richard P. Nuchols, and Warren P. Williamson, IV, which advantageously provides distinct closing and firing actions. Thereby, a clinician is able to close the jaw members upon tissue to position the tissue prior to firing. Once the clinician has determined that the jaw members are properly gripping tissue, the clinician can then fire the surgical stapler with a single firing stroke, thereby severing and stapling the tissue. The simultaneous severing and stapling avoids complications that may arise when performing such actions sequentially with different surgical tools that respectively only sever or staple.
One specific advantage of being able to close upon tissue before firing is that the clinician is able to verify via an endoscope that the desired location for the cut has been achieved, including that a sufficient amount of tissue has been captured between opposing jaws. Otherwise, opposing jaws may be drawn too close together, especially pinching at their distal ends, and thus not effectively forming closed staples in the severed tissue. At the other extreme, an excessive amount of clamped tissue may cause binding and an incomplete firing.
Generally, a single closing stroke followed by a single firing stroke is a convenient and efficient way to perform severing and stapling. However, in some instances, it would be desirable for multiple firing strokes to be required. For example, surgeons are able to select a length of staple cartridge for the desired length of cut from a range of jaw sizes. Longer staple cartridges require a longer firing stroke. Thus, to effect the firing, a hand-squeezed trigger is required to exert a larger force for these longer staple cartridges in order to sever more tissue and drive more staples as compared to a shorter staple cartridge. It would be desirable for the amount of force to be lower and comparable to shorter cartridges so as not to exceed the hand strength of some surgeons. In addition, some surgeons, not familiar with the larger staple cartridges, may become concerned that binding or other malfunction has occurred when an unexpectedly higher force is required.
One approach for lowering the required force for a firing stroke is a ratcheting mechanism that allows a firing trigger to be stroked multiple times, as described in U.S. Pat. Nos. 5,762,256 and 6,330,965. These known surgical stapling instruments with multiple-stroke firing mechanisms do not have the advantages of a separate closure and firing actions.
Other ratcheting surgical instruments are disclosed in commonly-owned U.S. Pat. No. 7,083,075, issued Aug. 1, 2006 to Jeffrey S. Swayze, Frederick E. Shelton, IV, Kevin Ross Doll, and Douglass B. Hoffman, entitled Multi-Stroke Mechanism With Automatic End of Stroke Retraction, which is herby incorporated by reference. Various embodiments disclosed therein employ a handle that produces separate closing and firing motions to actuate an end effector. In particular, the handle is configured to generate the firing force necessary to staple and sever the tissue clamped within the end effector through multiple actuations of a firing trigger. The device may further employ a linked transmission which reduces the required handle length, yet achieves a rigid, strong configuration when straightened for firing. A traction biased firing mechanism avoids binding in driving this straightened linked rack in cooperation with an anti-backup mechanism, with a lockout mechanism that prevents releasing the closure trigger during firing. Furthermore, an external indicator gives feedback to the surgeon as to how far firing has progressed, as well as providing a manual retraction capability. These embodiments also generally employ a relatively strong spring to automatically retract the cutting member after the end effector has been fired. While such designs are extremely effective, the use of the retraction spring requires additional firing force to be generated to overcome the opposing spring force during firing. This problem can also be somewhat exacerbated when using articulating end effectors. In particular, when an articulating end effector is employed, a larger return spring must generally be employed to retract the articulating firing member. Use of such larger spring further increases the amount of firing forces that must be generated to overcome the spring force and fire the end effector components.
Consequently, a significant need exists for a surgical stapling instrument having a multiple stroke or other type of firing mechanism that is equipped with a manually actuatable retraction mechanism and does not employ an additional retraction means such as a spring or the like that generates forces that must be overcome during the firing stroke.